Converting GPS coordinates to map coordinates

[Vern Potter]

Anybody know how to (or know of a book)on how to covert GPS cordinates to map coodinates and vice-versa?

[+Team Finn]

Try clicking HERE for a conversion site.

 

Dave

 

Me ambivalent? Well..... yes and no.

[Tahosa and Sons]

Know the meaning of datums and formats!!

I prefer to use UTM's and a Map from National Geographic Topo. Here is some help on UTM's.

http://www.maptools.com/UsingUTM/index.html

 

Tahosa - Dweller of the Mountain Tops.

[+Team Finn]

The site that Tahosa suggested should answer all your questions, it is clear and concise. Thanks Tahosa I bookmarked it too!

 

Dave

 

Me ambivalent? Well..... yes and no.

[+poksal]

If you want to change these...

N 28.5382, W 81.3796 (as in Streets USA) to

N 28° 32.292, W 81° 22.776 or Visa Versa

 

Then zap me an e-mail and I'll

send you a simple Excel sheet that

does them both ways... in a heart beat

 

but remember those first cords are from

an old system that has minor errors.

..a 100 foot error from the old survey is not uncomon.

 

...close enough for finding that old house or

historical favorite.

 

** The worst suggestion of a life time may be the catalyst to the best idea of the century, don't fail to listen to suggestions.

[+Poindexter]

Try this excellent book called "GPS Land Navigation" by Michael Ferguson Here's a link to Amazon.

 

http://www.amazon.com/exec/obidos/tg/detail/-/0965220257/qid=1040477722/sr=1-2/ref=sr_1_2/102-1747661-1972951?v=glance&s=books

 

Not sure really what your asking for. Basically, you need a map with grid lines or lat/lon graticules and a suitable "roamer" for plotting your position on the map. You must know the datum of the map. Let your GPS do the conversion from one datum to another as well as from one coordinate system to another.

 

Poindexter

www.geocities.com/fairbank56 (map printing help page)

[dsandbro]

I am losing confidence in jeep.com for coordinate conversion. Too many times the coordinates are off from the original. Sometimes right on, others several tens of meters. Not sure what algorithm that site uses. Spreadsheets may not be any more accurate, depending on method used, how many decimal places used in calculations, whether the creator used some built in spreadsheet functions, etc. (to save space and lines of code MS Excel and Quattro-Pro both use computational shortcuts in their built-in trig functions. These shortcuts may introduce small errors that compound in complex formulas. Not sure about Lotus 1-2-3). Use your GPS internal conversion.

[jfitzpat]

FWIW, there is no pure mathmatical conversion to NAD27, you have to use the ellipse, then the tables of empirical data.

 

That said, most GPS units will get you pretty close. The same with TRUE/MAGNETIC conversion. To really get it right, you should use the most recent published surveys, but most receiver firmware comes pretty close.

 

-jjf

[solohiker]

I let my gps do the conversion.

 

I enter coordinates from this site with WGS84 datum and Hddd MM.mmm format

 

I change the datum and format in my gps to match whatever datum and format my map was made with. Most USGS maps were made with NAD27 datum and UTM format.

 

When I get to a cache my typical deviation from cache coordinates to gps readout is within a ten meter radius. I use an old Garmin 12.

[+Alan2]

NADCOM for the most accurate conversion between WGS84(NAD83) and NAD27.

 

Alan

[+Poindexter]

NADCOM doesn't give coordinate conversion. I agree with Dave54, the first time I used jeep.com, it didn't give an accurate conversion and I haven't used it since. For a good on-line Datum and Coordinate conversion applet, try Maptran.

 

http://www.ualberta.ca/~norris/navigation/maptran.html

 

Not very user friendly, but it seems to be very accurate. Always agrees with my GPS anyway.

 

Poindexter,

www.geocities.com/fairbank56

[+writer]

Some of the suggestions for getting to the right datum (assuming that your map isn't using either WGS 84 or NAD83, which is the same in North America). However, if you are using a topographic map, why bother to convert to lon/lat? You can use the UTM coordinates that appear just below the lon/lat on the cache page. That lets you deal with horizontal and vertical linear measurements, and not the weirdness you need with a lon/lat ruler.

[+Poindexter]

I didn't see where anyone in this thread was talking about using lat/lon with a topographic map. And you can't use those UTM coordinates provided on the cache page with most topo maps because those coordinates are for WGS84 datum and most topo maps use NAD27 so you still have to do the conversion. Just let the GPS do the conversion for you and make sure you know the datum of the topo.

 

Poindexter

[+writer]

quote:

---

Originally posted by Poindexter:

I didn't see where anyone in this thread was talking about using lat/lon with a topographic map. And you can't use those UTM coordinates provided on the cache page with most topo maps because those coordinates are for WGS84 datum and most topo maps use NAD27 so you still have to do the conversion. Just let the GPS do the conversion for you and make sure you know the datum of the topo.

 

Poindexter

---

 

The original question was: "Anybody know how to (or know of a book)on how to covert GPS cordinates to map coodinates and vice-versa?" If the person wasn't trying to use a map, then there would be little need, I suspect, to convert anything.

[+Poindexter]

Writer, you said: However, if you are using a topographic map, why bother to convert to lon/lat?

 

I didn't see where anyone was talking about converting to lat/lon. And I guess you could use those UTM coordinates on the cache page as long as you set your GPS's datum to WGS84 before inputting them manually and then set it to NAD27 to use with the topo map.

 

Poindexter

[+writer]

quote:

---

I didn't see where anyone was talking about converting to lat/lon. And I guess you could use those UTM coordinates on the cache page as long as you set your GPS's datum to WGS84 before inputting them manually and then set it to NAD27 to use with the topo map.

 

Poindexter

---

 

Actually, people have talked about a whole range of things because the original question was not specific. Lat/lon is certainly one type of "map" coordinate the original poster might have wanted. But it's impossible to say.

 

Assuming that anyone would have to convert anything is a fallacy, by the way. There are some maps that use WGS 84. (NAD83 is the same thing.) There are even other datums in the US - like NAD29. If you go elsewhere in the world, NAD27 or 29 won't do a bit of good.

[thueringen-scout]

I can give you a small self written tool for PC's. It is a calculator (appears similar like the Windows calculator) that is able to convert LAT/LONG coordinates in decimal format into degrees/minutes/secons and vice versa. If you need it just contact me: kaiwick@web.de

[2oldfarts (the rockhounders)]

Hope this is what you're looking for.

GPS coordinates are map coordinates. Look at the map legend and find out what datum the map is based on and set your GPS to the same datum. If you need to change from Lat. & Long. to UTM then most GPS units will do that.

If you have a Magellan Meridian unit then you can set the main page top section to Lat.& Long. of the desired datum and set the bottom section to any other coordinate system and datum of your choice.

[Cache Canucks]

If your GPSr offers you the option of selecting the MGRS format for displaying position, that's probably the best means of locating where you are on a hardcopy topo. If you aren't familiar with how to manually plot a position on a map using the military grid reference system, it's a breeze to learn (and a whole lot easier than struggling with lat/lon ...which is why the military uses it).

[+TippySheep]

I know this is an old thread, but I'll try anyway.

 

I'm looking for an excel spreadsheet that will convert lat and long, entered in two seperate cells, into a ONE cell WGS84 Datum expression.

 

I've found a spreadsheet that will do it but it takes 4 cells to express the WGS84 Datum.

 

And no, having my GPS convert it isn't an option at this point. I need to do about 500 conversions for campgrounds. I'm adding GPS coords to my website so my users can a. use the coods, and B!!! I link through to geocaching.com

 

Help please!

[gfletts]

I know this is an old thread, but I'll try anyway.

 

I'm looking for an excel spreadsheet that will convert lat and long, entered in two seperate cells, into a ONE cell WGS84 Datum expression.

 

I've found a spreadsheet that will do it but it takes 4 cells to express the WGS84 Datum.

 

And no, having my GPS convert it isn't an option at this point. I need to do about 500 conversions for campgrounds. I'm adding GPS coords to my website so my users can a. use the coods, and B!!! I link through to geocaching.com

 

Help please!

 

I'm a surveyor, and we use a program that comes from the Corps of Engineers to convert coordinates/state plane coordinates (map coordinates). this program can be found at this web site and the program name is Corpscon. You can convert between UTM,geographic,state plane and between differnt datums. Here is the link: "http://crunch.tec.army.mil/software/corpscon/corpscon.html".

 

Greg

[+fizzymagic]

I know this is an old thread, but I'll try anyway.

 

I'm looking for an excel spreadsheet that will convert lat and long, entered in two seperate cells, into a ONE cell WGS84 Datum expression.

Are the lat and lon WGS84 values, or some other datum (I don't mean format, I mean datum). By format, I mean like decimal degree values...

 

If they are, then what you ask will be no problem.

[+TippySheep]

I THINK I got it figured out:

 

They were lat and long in a decimal format. I found a spreadsheet that will convert them to the datum I'm looking for. I also had to figure out how to get them into a one-cell output from the 4 cells that it converted into. It was complicated but I think it'll work.

 

Thanks for your help. And, I'll check out that spreadsheet!